1. Ch. 43 – the immune system Essential Knoweldge 2.D.4 (a-b)
Big Idea 2

2. What you must know: Several elements of an innate immune response
The differences between B and T cells relative to their activation and actions.
How antigens are recognized by immune system cells
The differences in humoral and cell-mediated immunity
Why Helper T cells are central to immune responses

3. Chapter 43 Warm-Up Define the following terms:
Pathogen – a bacteria or virus
Antigen –  the protein on the surface of a cell (bacterium, fungus or virus) that our bodies recognize as a foreign substance and triggers the immune system into producing antibodies specific to that antigen
phagocytosis (cell eating)
Phagocytes – types of white blood cells that ingest invading organisms and initiate the inflammatory response
Macrophages - a specific type of phagocyte found throughout your body -eat the antigens; this causes swelling. Macrophages secrete lysosomes into the antigen to destroy it; problem – it will attack anything not us, including organ transplants
lymphocytes – types of white blood cells

4. Overview
A virus uses the machinery of your cells to make more copies of itself, until it destroys the cell; when that happens, the cell bursts and releases all the new viruses into your body to repeat the process
Without the immune system, we’d be in big trouble.

5. Types of Immunity Adaptive Immunity (humoral or cell mediated)
Innate Immunity (skin, phagocytes)
Adaptive Immunity (humoral or cell mediated)
Non-specific
Present at birth (passed from mother through placenta)
All plants & animals
Rapid response (fever, inflammation, etc)
Pathogen-specific
Develops only after exposure to inducing agents (virus, bacteria, etc)
Only in vertebrates
Involves B and T cells

6. Plant Defenses
Nonspecific responses (have no immune system response) – it kills anything that invades or moves inside the organism
Receptors recognize pathogen molecules and trigger defense responses
Thicken cell wall, produce antimicrobial compounds, cell death
Localize effects

7. Plant and Animal defense mechanisms – Innate Immunity
Hypersensitive response (a plant can sense proteins given off by bacteria by using its “R” gene) – reminder from ch. 39, plant responses
Lets off an oxidative burst, that kills the cells, even if it’s not infected
It also gives off a protein that changes the cell walls of all the adjacent cells
Doesn’t have memory, so it will go through the same process if it’s infected again

8. Innate Immunity - How Immunity Works - Skin
This is the first layer of defense
Creates a barrier
Has a low pH (which makes it hard for some bacteria to live there)
Chemicals on the surface of our skin disrupt certain viruses
Bacteria (normal flora which just lives there) crowd out our skin which makes it hard for other substances to enter
Certain cells of the mucous membranes produce mucus
A viscous fluid that traps microbes and other particles

9. Skin cont.
If you get a cut, then there is a breach in your first defense
Internal cellular defenses
Depend mainly on phagocytosis (cell eating)
Phagocytes ingest invading microorganisms
Initiate the inflammatory response
Inflammation occurs (chemicals are released that causes our body to respond)
For example – acne (an infection in the pores of your skin)– bacteria are living and eating under our skin
Macrophages (a specific type of phagocyte found throughout your body) enter and eat the invaders; this causes swelling. Macrophages secrete lysosomes into the antigen to destroy it
problem – it will attack anything not us, including organ transplants

10. Phagocytosis

11. Inflammatory Response

12. Lymphatic System: involved in adaptive immunity

13. Adaptive Response
Lymphocytes (WBCs): produced by stem cells in bone marrow
T cells: mature in thymus
helper T, cytotoxic T
B cells: stay and mature in bone marrow
plasma cells  antibodies

14. Aquired Immunity - Specific immune response
Specific immune responses mean that we have generated antibodies for a specific virus, so we won’t get the same cold twice
Pathogens have specific proteins on their surfaces (antigens)
To fight them, we have structures called antibodies (proteins produced by our bodies)
They have very specific shapes that will allow them to connect to the antigen; this helps the macrophages find them, and it also makes it harder for the antigens to do their job

15. Specific Immune Responses Cont. – B lymphocytes
B Lymphocytes are 1 type of white blood cells or phagocytes (attack viruses in our bodies)
Made in bone marrow
Create a humoral response (means, “in the fluid” or in the “humors” – like blood, lymph material, insterstitial fluid)
A naïve B cell senses the shape of the antigen, sends out a chemical message, and the B lymphocytes produce the antibodies specific for that antigen
Memory B cells are then created to help give us immunity for the rest of our lives

16. Specific Immune Response cont - T Lymphocytes
T Lymphocytes target and kill the cells that are already infected (responsible for what’s called a cell-mediated response)
Created in the thymus (a gland on top of our heart; this is where they get the “T” from)
Create Killer T Cells or Cytotoxic T Cells (a type of T lymphocytes) which target cells that are infected, docks next to them, and kills them
Causes cell death

17. Major Histocompatibility Complex (MHC)
Proteins displayed on cell surface
Responsible for tissue/organ rejection (“self” vs. “non-self”)
B and T cells bind to MHC molecule in adaptive response
Class I: all body cells (except RBCs)
Class II: displayed by immune cells; “non-self”

18. Helper T Cells
You have an antigen that is eaten by a macrophage, which chops up the antigen and produces pieces of it on it’s surface using a chemical called MHC2 (major histocompatibility complex); you then get a Helper T cell (another type of T Lymphocyte) which docks on the macrophage and senses the shape of that antigen using another chemical called CD4; this initiates both the humoral and cell-mediated responses
A Helper T cell tells the shape of the antigen to the B cells so they can make more antibodies, tells it to the macrophages which will then eat the invaders, and they activate the killer T cells so they can kill the infected cells
Helper T cells basically initiate the entire immune response
Acquired immunodeficiencies range from temporary states to chronic diseases
These are the cells that are being infected by HIV

19. Antigen: substance that elicits lymphocyte response
Antibody (immunoglobulin – Ig): protein made by B cell that binds to antigens

20. Cell-Mediated Immune Response Humoral Immune Response
Antigen-presenting cell
Cell-Mediated Immune Response
(T Cells)
Humoral Immune Response
(antibodies)
Helper T cell
B cell
Cytotoxic T cell
Plasma cell
tag for destruction
Identify and destroy
Infected cell
Antibodies

21. AIDS
People with AIDS are highly susceptible to opportunistic infections and cancers that take advantage of an immune system in collapse
You don’t die from aids, you die from a secondary infection
Because AIDS arises from loss of helper T cells, it impairs both the humoral and cell-mediated immune responses
The loss of helper T cells results from infection by the human immunodeficiency virus (HIV)

22. Pathogens (such as bacteria, fungi, and viruses)
INNATE IMMUNITY (all animals)
Barrier defenses:
Skin Mucous membranes Secretions
Recognition of traits shared by broad ranges of pathogens, using a small set of receptors •
Internal defenses:
Phagocytic cells Natural killer cells Antimicrobial proteins Inflammatory response
• Rapid response
Figure 43.2 Overview of animal immunity.
ADAPTIVE IMMUNITY (vertebrates only)
Humoral response:
Antibodies defend against infection in body fluids.
Recognition of traits specific to particular pathogens, using a vast array of receptors •
Cell-mediated response:
Cytotoxic cells defend against infection in body cells.
• Slower response

23. Autoimmune Diseases
In individuals with autoimmune diseases, the immune system loses tolerance for self and turns against certain molecules of the body
Rheumatoid arthritis is an autoimmune disease leading to damage and inflammation of joints
Multiple Sclerosis

24. Blood Types
Antigens on red blood cells determine whether a person has blood type A (A antigen), B (B antigen), AB (both A and B antigens), or O (neither antigen)
Antibodies to nonself blood types exist in the body
Transfusion with incompatible blood leads to destruction of the transfused cells
Recipient-donor combinations can be fatal or safe

25. Cancer and Immunity
The frequency of certain cancers increases when adaptive immunity is impaired
20% of all human cancers involve viruses
The immune system can act as a defense against viruses that cause cancer and cancer cells that harbor viruses
In 2006, a vaccine was released that acts against human papillomavirus (HPV), a virus associated with cervical cancer

26. Immunological Memory Primary immune response: 1st exposure to antigen
Memory cells:
Secondary immune response: repeat exposure  faster, greater response

27. B cells that differ in antigen specificity Antigen Antigen receptor
Figure 43.14
B cells that differ in antigen specificity
Antigen
Antigen receptor
Figure Clonal selection.
Antibody
Memory cells
Plasma cells

29. Passive immunity: via antibodies in breast milk
Immunizations/vaccines: induce immune memory to nonpathogenic microbe or toxin
Passive immunity: via antibodies in breast milk
Allergies: hypersensitive responses to harmless antigens
Autoimmune Diseases:
Lupus, rheumatoid arthritis, Type I diabetes, multiple sclerosis
HIV: infect Helper T cells
AIDS = severely weakened immune system

30. Secondary Exposure
If you are exposed to a virus that you have previously experienced, you would already have antibodies, memory B and Memory T cells that can be quickly produced and fight off the cold before you feel its effects.

31. Virtual Lab